Production of improved cellulosic materials



Sept. 5, 1950 R. E. REEVES 2,520,963

PRODUCTION OF IMPROVED CELLULOSIC MATERIALS Filed June 6, 1947 COPPER NUMBER m 0 IO 20 3O 4O 50 6O FLUIDITY RHES FLUIDITY RHES N b O O 0 INVENTOR.

HWRS R.E.REEVES BY giwm Patented Sept. 5, 1950 2,520,963 I rnonuc'rron or meaovan CELLULOSIC MATERIAL Richard E. Reeves, New Orleans, La., alsignor to the United States oi America as represented by the Secretary oi Agriculture Application June 6, 1947, Serial No. 753,121 6 Claims. (01. 260-212) (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) This application is made under the act of March 3, 1883, as amended by the act of April 30, 1928, and the invention herein described, 11' petented, may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment to me 01' any royalty thereon.

This invention relates to the production of cellulosic materials having improved resistance against attack by chemical reagents, especially alkalies.

According to this invention, when cellulosic materials are treated with an anhydrous alcohol containing an anhydrous acid, or acid with very limited amounts of water as catalyst, there occurs a cleavage of certain linkages in the cellulose molecule to form modified cellulose containing alcohol bound in chemical union. This reaction is hereafter called -alcholysis," or spe-. cifically, methanolysis or ethanolysis, where the alcohols employed are methanol or ethanol, respectively. The products of alcoholysis of cellulose difler from modified celluloses of equal molecular size prepared in other manners, by possessing remarkable resistance against reaction with dilute aqueous alkalies, either hot or cold.

Cellulose in an essentially dry state (such as air-dried or oven-dried) reacts at ordinary temperatures or at elevated temperatures with remarkable rapidity with a solution prepared by dissolving an anhydrous acid such as hydrogen chloride in an anhydrous alcohol such as commercial anhydrous methanol. product is essentially free from combined acid, but contains traces of very firmly bound alcohol which may be liberated by drastic aqueous acid hydrolysis, or may be determined as alkoxyl groups in the usual manner. The product, in the cases of methanol or ethanol, is a colorless white powder exhibiting many of the usual cellulose reactions such as xanthation, nitration, and acetylation to give products analogous to those produced from cellulose, except that such products are usually of lesser molecular size than similar ones obtained from unmodified cellulose. Alcoholyzed cellulose is soluble in cellulose solvents such as cuprammonium hydroxide solution, cupraethylenediamine solution, or certain quaternary ammonium hydroxide solutions. (The optical behavior of the cuprammonium solution is indistinguishable from that of cellulose itself.) However it differs from cellulose modified by other reagents such as aqueous acids or oxidizing agents, by having essentially no reducing action towardalkaline copper solutions and low reactivity toward, or low solubility in, dilute alkalies of all sorts.

If the alcoholysis reaction be carried out similarly, but in the presence of as little as percent The resulting water, then the reaction is appreciably slower and takes a diiferent course. The product differs from that obtained under essentially anhydrous conditions by having a measurably large reducing action toward alkaline reagents.

As stated above, in contrast with other methods of reducing the size of the cellulose molecule. alcoholysis does not produce an increase in the so-called reducing value of the modified cellulose. This behavior is illustrated in Table I and Figure 1, wherein reducing value is measured in terms of "copper number by a known procedure of T. F. Heyes (J. Soc. Chem. Ind. 4'7T, 90 (1920). Included in this exhibit are cellulose preparations modified in one instance by methanolysis in absolute methanol (curve A); in a second case by reaction in methanol containing 10 percent by volume of water (curve B); and finally modification by aqueous acid (curve C), a well known procedure, for producing so-called hydrocellulose. The cuprammonium fluidities were measured by the method of the British Fabrics Research Committee (Fabrics Research Committee. The viscosity of cellulose solutions. H. M. Stationery Ofllce, London, 1932) at 25 C. and employing a cellulose concentration 01' 0.5 percent. (All copper numbers reported herein were made by the aforementioned method of Heyes, and all cuprammonium fluidities were determined by the latter method'using either 0.5 or 2.0 percent cellulose concentrations, the concentration being noted in each instance. In all fluidity measurements save on series, which is ,duly noted, the

' cuprammonium solvent contain'ed 15 grams of copper and 240 gramsot ammonia per liter, and the temperature of measurement was 25 C. All fluidities are expressed in terms of rhea-reciprocal poise.)

Table I (Anhydrous MeOH-HzO MeOH-HCI) (0:l)HCl) (mo-3C1 H150) Fluidity g? Fiuidity QF Fluidity W 0- 1 O. i O,

6.8 p. 30 4. 4 0.16 3. 9 0.36 13.0 .24 5.9 .24 5.6 .31 24.4 .33 11.2 .35 9.7 .56 37. D 30 19. 3 5O 13. 7 43.0 .27 35.1 .95 16.0 I .84 63. 7 25 20. 8 1. 16 51. 1 1o 21. 9 1. s5 37. l 2. 18 46. 7 3. 6 5s. 5 4.5 54. 5 5. 1

Inspection of Table I and Figure 1 shows that crease in fluidity. (This increase is even more pronounced if any or the oxidizing reagents such as sodium hypochlorite, periodic acid, dichromate, and so forth, be employed to increase the fluidity.) An intermediate, but neverthele s pronounced increase in reducing value is observed it the cellulosic materlal'be treated with catalyst and methanol containing pereentwater. The copper number of the untreated cellulosie material was found to be approximately 0.30. Columns 1 and 2 give the fluidity and copper number for diflerent methanolyzed cellulose preparations which were prepared using anhydrous methanol- HCl reagent. Columns 3' and 4 give the corresponding values when the reagent was methanol containing 10 percent by volume of water and HCl as catalyst. Columns 5 and 6 list-various "hydrocelluloses (fluidities and copper numbers, respectively) prepared by treating cellulose with water containing HCl or H2804. All fluidity determinations reported in Table I were made using 0.5 percent cellulose concentrations.

When the alcoholyzed cellulose is compared with hydrocellulose of approximately equal ouprammonium fluidity, as was done in the preceding table and figure, the striking diflerence in the relationship between fluidity and copper number becomes apparent. The extremely low cop per number oi the highly degraded alcoholyzed material indicates almost complete absence of reducing groups. This is most simply explained by assuming that cleavage of the cellulosic chain involves hemi-acetal formation of the potential reducing group at the point of rupture illustrated by structure I in the accompanying diagram. A second possibility, which our experimental data does not exclude, is that the reducing groups are converted to acetals (structure II).

A second characteristic sharply distinguish. ing alcoholyzed tellulose irom other modified cellulosesis the low solubility of the alcoholyzed material in hot, dilute alkali. This is in sharp contrast with the behavior of highly degraded hydrocellulo'ses. A comparison 0! the solubility of the two typ of celluloses is give in Table II. Since it is doubtful if true solubility could be influenced greatly by attachment of a single methoxyl group to a molecule composed of forty or more glucose units, it seems likely that the solubility oi hydrocellulose is due to chemical reaction between the hot alkali and the reducing groups while the relative insolubility of the alcoholyzed material is due to the absence of reducing groups. Both the extensively hydrolyzed and alcoholyzed celluloses gelatiniz'e in cold concentrated alkali under the conditions of alpha cellulose determination;

Aronovsky and Dryden (Argnovsky, S. I., and E. C. Dryden. The Paper'Industry and Paper World. June. 1940) and Lynch, D. F. J. Ind. and Eng. Chem. 22, 952 (1930)) have shown that for many cellulosic materials solubility in the nitrators test (7.14% NaOI-I at C.) is slightly higher than, but parallel to; solubility under the conditions of alpha cellulose. determination. However, the alcoholyzed materials which disperse almost completely in 17.5 percent sodium drydroxide solution show only 4 to 7 percent solubility in the nitrators test.

Table II nydmeeuulose Alcohol :sed Cellu- Fluidity {3; 35 Fluidity @123 1a 9 4. 9 13.8 2. 3 20. a a a 1 1. 2 26.7 as 39.1 1.3 29.1 12 1 4410 1.3 36.0 18.8 49.1 I 1.0 sec 21.5 53.1 1.3 41.8 29.2 50.5 24 4 34.6 40.3 39.2

In Table II is shown, in columns 1 and 2, data on hydrocellulose from a typical experiment reported by Davidson (Davidson, G. F. J. Textile Inst. 34'1', 8796 (1943) In column 1 are given cuprammonium fluidities, and in column 2 the percentages soluble in hot dilute aqueous alkali, for hydrocelluloses with 10 N H1804 at 20 C.

per liter, and at a temperature or 20C. We have determined in separate experiments, however, that fluidities determined under such conditions do not difl'er by more than ai'ew percent from those obtained under the conditions we have employed, and the diflerence would in no wiselbe suflicient to render invalid the conclusion which may be drawn from Table'II, namely. that alkali i mei'cerized) approached. Upon alcoholysis or hydrolysis of mercerized cellulose a higher fluidity may be obtained than is possible with "native (not cellulose. With. the inercerized cellulose alcoholysis seems to'give a slightly higher maximum fluidity than does hydrolysis.

Table III i 2 a a 4 5 a J v Hydrolysis 3 Alooholysis Lossin Fluidity Loss in Fluidit weight 2%) Tmtmm weight 2 y Native Cellulose 0.900 N H01: Per cent 0.28 N H0] in MeOH: Per cent r 1. l 13 0 24 2 1 h 100 7 22.0 IX, 3. 4 24 2 hr. 120... 31. 0 24. a 1 hr. 120 f 6.0

' 0.55 N H01 in MeOH a 4 l 1112, 120. 6.0 24.9 4 hr., 120 1. 3 2s. 0

Mercorized Cellulose 0m N 1101: 0.28 N 1101 in MeOH: 1

2 hr., 100 1. 1 1 hr.. 65".--- 33. 0 2hr. 120%.... 1a 0 31.1 1 hr., so 1.7 so. 1 1.00 N 3101, a 24. a sea 1 hr., 100 a. a 41. 1

hr., 120. 1 hr 120 3. 0 41.3 0.55 Nhfliqlzin MeOH:

a 1 i 42 4 4 ha: 120 a 1 4a 2 solubility is much less for alcoholyzed cellulose than it is for hydrocellulose of approximately the same fluidity. Column 3 gives the fluidity we have determined for diflerent methanolyzed cellulose preparations, and column 4 gives the corresponding alkali solubility. Fluidities in columns 1 and 3 were determined at 0.5 percent cellulose concentration; and alkali solubilities in columns 2 and 4 were determined by keeping a weighed sample of the modified cellulose in approximately 100 parts of'l percent aqueous sodium hydroxide solution for 6 hours in a boiling water bath, followed by filtering oil the insoluble (.0

portion, and subsequent washing. drying. and weighing operations.

It has been shown (Davidson, G. F., J. Textile Inst. 34T, 87/96 (1943)) that when cellulose is hydrolyzed with aqueous acids the cuprammonium o5 The situation suggests that the cellulose molecule when degraded below a certain limit either passes into solution or disappears because of increased susceptibility to further hydrolysis. Likewise with alcoholysis a limiting fluidity is approached and more drastic treatment results in loss of Table III is divided into six columns the first three of which record the treatment, loss of weight upon treatment, and fluidity of the hydrocelluloses, respectively. These hydrocelluloses were prepared from out cotton fiber which had been purified by a commercial firm. Some oi! the experiments were made on the native purified fiber, while some 01'- the experiments were made subsequent to a so-called mercerizing treatment similar to the one described later under Example 5. Columns 4, 5, and 6 of Table III give the treatment, loss of weight on treatment and fluidity of alcoholyzed preparations, made from low viscosity linters purified by a commercial firm. Some of the acoholyzed experiments were likewise carried out on the linters following a mercerizing treatment. All fluidities reported in Table III were measured on 2.0 percent dispersions of cellulosic material. The experiments are arranged in Table III, for both native and mercerized celluloses, in the order of 'hisn ing fluidity value was estimated by viscometrie methods. The weight average degree of polymerization, calculated from the intrinsic viscosity by the method of Kraemer (Kraemer, E. 0., and

J. B. Nichols. The Ultracentrifuge by the Bvedberg and K'. O. Pedersen. pxford. 1940. p. 420.) yielded values of 132 and 73 glucose units, respectively. The data for obtaining the intrinsic viscosities are given in Table IV.

Methoxyl analysis of cellulose and alcoholyzed cellulose made by a. standard method (A. 0. A. C. Ofllcial and tentative methods of analysis XLI. th ed. p. 647-8 (1940)) show that methanolysis introduces a small amount of bound methoxyl. (Attempts to remove this methoxyl by long-continued washing or refluxing with water were unsuccessful.) Although even purified cotton linters gives a small apparent" methoxyl value, due possibly to hexyl iodide formed by the action of hydriodic acid upon the glucose liberated during the determination, methanolyzed native and mercerized celluloses gave measurably higher methoiwl values. Accordingly, the analyses of methanolyzed cellulose given in Table V should be corrected by substracting the 0.32 percent "apparent methoxyl" content of the purified cellulose. When this is done there remain 0.22 and 0.52 percent methoxyl, respectively, corresponding to number average degrees of polymerization of 87 and 3'7 glucose units for the native and mercerized celluloses, respectively. The difference between the weight average degree of polymerization determined by analysis is not surprising. Rather it lies in the direction, and is of the order of magnitude, to be expected of a non-homogeneous mixture of molecular sizes such as is invariably encountered in cellu- 1 Low viscosity purified linters, native and mercerized, were treated for 1 hour at 120 with 0.5 N HCl in MeOH.

1 The cuprammonium hydroxide solution contained 15 g. Cu and 240 2:. NH: per i.

I The limit SI i100 was determined by straight line extrapolation These dis rsions were prepared with exclusion 01 air, but the transfer to stwald type viscometer and the measurements were gall without exclusion of air. The measurements were made at able V Substance analyzed age? 0. 83 34 v .sa Purified cotton lintsrs... :gi .29 28 .32

Average 0. 82

, o. 02 Methanoiyzed native cotton cellulose I? 64 Average '0. 54

. 0. 82 Methanolyzed memorized cotton cellulose g I 85 Average 0. 84

Alcoholyzed cellulose may be used in a variety of ways analogous to the uses of otherwise modified celluloses. It is especially useful in those products which require a relatively small average molecular size for the cellulosic constituent, such as' the cellulose'nitrates for lacquers and plastics, because in these products large molecular size is associated with unwieldy viscosity characteristics. Also in the production of cellulose xanthate used in the production of rayons and films, it is common practice to age the alkali cellulose until it has become reduced to an optimum molecular size. By employing the alcoholyzed cellulose, described in our examples, in this process it is possible to obtain the desired molecular size rapidly prior to alkali cellulose formation, and

furthermore the remarkable resistance of alcoholyzed cellulose against alkaline reagents results in an improved yield and an improved product.

The process has been carried out principally using purified cotton fibers, but it has been found to be equally effective with raw cotton fibers, cotton linters, and with cellulose derived from wood pulp. It is also effective with cellulosic materials which have been pretreated with strong aqueous alkalies.

The process is more specifically exhibited in the following examples:

EXAMPLE I In this example is exhibited alcoholysis at ordinary temperature with methanol and ethanol. For comparison are included the reaction in the presence of percent methanol and 10 percent water, and the reaction in water-all catalyzed by 0.5 N HCl. Commercial grades of absolute alcohols were used without further purification in this and subsequent examples.

The cotton fiber used in this example had been mechanically cleaned in a Shirley analyzer. It was then extracted in a Soxhlet extractor for four hours with hot alcohol, then boiled, for eight hours with water. The fiber was subsequently air-driedand was used in this condition, it having been found in separate experiments that the small amount of moisture introduced with the sample did not cause a detectable change in the course of the reaction. Parallel experiments were I set up employing hydrochloric acid in absolute.

methanol, absolute ethanol, methanol-water (9:1 by volume), and water, each containing-H01 in u 0.5 N concentration. Samples of cotton fiber HCI, by weight.

, periments are shown in Table VI. In column 1 is given the duration of the treatment in hours, in column, 2 the fluidity of the methanolyzed. samples, in columns 3, 4, and 5 the fluidities of those treated in 90 percent methanol, absolute ethanol, and water, respectively. All fluidities in this table are at 0.5 percent cellulose concentration. The blank spaces indicate that no experiment was run for that particular time and solution.

Inspection shows that the rate of reaction is greatest in the case of absolute methanol-HCI, slightly less for ethanol-HCI, intermediate for 90 percent methanol-HCI, and least for water-HCI. The fluidity of the original cotton fiber was 2.4 rhes, and since molecular size is inversely related to fluidity it is apparent that the size of the cellulose decreased much more rapidly upon alcoholysis than upon hydrolysis with the aqueous acid.

The results of this experiment are also shown graphically in Figure 2, except that the run employing ethanol is omitted since it so closely parallels the one with absolute methanol. In Figure- 2 is shown the cuprammonium fluidity of cellulose previously treated at 20 for various lengths of time with 0.5 N HCl in absolute methanol- (curve A) with 0.5 N HCl in 90 percent methanol (curve B); and with 0.5 N HCl in water (curve EXAMPLE II Raw cotton fiber was placed in absolute methanol containing one percent anhydrous This suspension was heated under refiux at the boiling temperature and samples of fibers were withdrawn at intervals of 10 minutes and 1 hour. After four hours the refluxing was discontinued and'the remaining insoluble material constituted a. third treated sample. water until free of acid and then air-dried in the atmosphere for at least 48 hours before cuprammonium fluidity determinations were made. These results are shown in column 3 of Table VII. The value for the 10 minute treatment was obtained using a cellulose concentration of 0.5 percent, while those of the 1- and 4-hour samples mployed a 2.0 percent concentration. In column 1 of Table VII is given the time of boiling, and in column 3 is given the copper numbers of the treated samples determined by the method of Heyes.

All the treated samples were rinsed with Table VII Time of refluxing jlujdjty C0 9 1' Inspection of Table VII shows that as methanolysis progresses at this elevated temperature, there is no corresponding increase in reducing value as measured by copper number.

Table VIII 1 2 a Reagent Fluidity 25,?"

Methanol-H180 mum-moi. 31

EXAMPLE III Cotton fiber, extracted as in Example I and air-dried, was treated in the following manner. Two samples of cotton fiber (3 gm. each) were placed in 250 ml. flasks with (a) about 150 ml. abs. methanol containing sulfuric acids and (b) about 150 ml. of abs. ethanol containing sulfuric acid. (The acid-alcohol reagents were prepared by adding 2.08 ml. concd. sulfuric acid to the particular alcohol and making up to a volume of 200 ml. with the alcohol. Anhydrous sulfuric may also be used.) The flasks containing reagent and flber were placed in a water bath maintained at 25 C. for 48 hours after which the samples were removed and washed in distilledv EXAMPLE IV Twenty grams of commercially purified lowviscosity cotton linters were placed with 250 ml. of methanol containing one percent HCl in a glass-stoppered bottle. The bottle and contents were placed in a steel autoclave containing the same alcohol and the autoclave was closed tightly. The temperature of the autoclave was raised to 0. (about 42 pounds per square inch pessure) and maintained at that temperature for one hour. At .theend of this time the autoclave was allowed to cool and the powdery cellulosic product was filtered on a sintered glass filter and washed on the fllter with ethyl alcohol until free from acid. The material was finally rinsed with diethyl ether andsubsequently dried in a current of air heated to F. The yield was 18.7 ams. The cuprammonium fluidity of the product was 23.0 rhes in 2 percent dispersion.

Sixteen grams of this product when nitrated under standard conditions with a mixture of HNOs-HzSO4-H2O gave 22.2 grams of a nitrate containing 11.6 percent nitrogen and exhibiting a nitrate viscosity of 135.5 centipoise when 6.1 grams of the, substance were dissolved in a mixture composed of 11 grams of ordinary alcohol, 8.75 grams ethylacetate, and 24.15 grams of toluene. This product corresponded in appear- 1 11' ance, viscosity, and stability very closely with a widely used commercial cellulose nitrate.

' EXAMPLE V Twenty grams of commercially purified lowviscosity cotton linters were treated for one-half hour at room temperature with about 300 ml. of 18 percent aqueous sodium hydroxide. The fiber was transferred to a filter and washed with water until the washings were neutral. The fiber was then treated for 20 minutes with dilute aceticgacid and subsequently washed free of acid with water.

After squeezing out most of the water the remaining water was displaced by six successive changes of absolute methanol. The mercerized linters were then placed in a glass jar in an autoclave (as in Example IV) with 300 ml. of methanol containing one persent HCl and heated to 120 C. for 1 hour. The acid was removed as in Example IV, however the sample was dried by' exposure to the atmosphere for 48 hours. The cuprammonium fluidity of this preparation was 40.2 rhes in 2 percent dispersion. The copper number was 0.18. The yield of material was 18 grams and the product contained 6 percent moisture by weight.

EXAMPLE VI Thirty grams'of commercially purified wood pulp were treated in an autoclave (as in Example IV) with 490 ml. of methanol containin 2 percent HCl for one hour at 120 0. Also 30 grams of the same material was mercerized as in Example V and treated exactly as the preceding sample. Both were washed free of acid EXAMPLE VH Anhydrous H01 was ledseparately into npropanol, n-butanol, and n-amyl alcohol to give solutions containing 9.44, 9.33, and 10.43 percent HCl, respectively, as determined by direct titration with standard alkali. These stock solutions were diluted with the proper alcohol to form the acid-alcohol solutions used in the following experiments. Ten or twenty gram samples of purified cut cotton fibers were treated in the autoclave (as previously described) at 120 with I the solutions and for the duration noted in column 1 of Table IX.

In column 2 is given the percent loss of weight during alcoholysis, in column 3 is given the fluidity (2 percent cellulose concentration), and in column 4 is noted the appearance of the preparation.

Table IX Loss in Treatment at 120 0. weight, ay Appearance 1 percent p 1 In propanol:

30 min. 0.57 HCL. 6.0 17.9 30 min; 1.09: no] 9.0 19. 2 r g g I 1 hr., 2.0% H01 18.0 23. o

In butanol" 30 min 0.5% H01 2. l7. 9 1 hr., 2.0? H01 l6. 0 18. 9 brown powder. 4 hit, 2.0 0 H01. 16. 6 3. 9 In amyl elco ol:

., a 0i i9. 0 22. 2 dark brown.

g The above examples are not to be construed as exhausting the scope of the invention. It is within the purview of the process to employ mixtures of the alcohols, viz., mixtures of two or more of the alcohols, methanol, ethanol, n-propyl, isopropyl, butyl, iso-butyl, amyl, and so forth. -Aralkanois such as benzyl alcohol may also be employed.

Other acids may be employed, viz., p-toluenesulfonlc acids may be substituted for hydrochloric and for sulfuric in each of the above examples. A 2-normal acid solution is the preferred upper limit) The alcoholized cellulose also may be used as a sizing material in textile finishing.

EXAMPLE VIII Thirty grams 01. high viscosity cotton linters were treated with one liter of absolute methanol 7 containing 0.5 N anhydrous HCl for 20 hours at approximately 23 C. The fiber was removed on a filter and 915 ml. of the alcoholic acid solution was recovered. The moist fiber was next rinsed free from acid with water and treated on the filter with 300grams 01 18 percent aqueous sodium hydroxide solution. After 10 minutes the alkali was drawn oil by suction and the fiber was pressed and sucked as dry as possible. The weight or the alkali cellulose at this point was grams. This was placed in a stoppered bottle with 15 ml. of carbon disulfide and the bottle was rotate]. on a small mill for 4 hours during which time xanthation took place. Next excess CS: was removedand 300 mi. oi 4.5-percent sodium hydroxide solution was introduced and the milling continued until solution was complete. After a ripening period of 4 days the xanthate solution was filtered through a sintered glass filter and extruded into a suitable acid coagulating bath composed of sulfuric acid, 8 parts; glucose, 10 parts; sodium sulfate, 12 parts; zinc sulfate, 1 part, and water, 69 parts. The filaments, after being washed, stretched, and dried in the usual manner, were of excellent quality. Note that the process involving methanolyzed cellulose entirely omitted the ageing of alkali cellulose now customary in the manufacture of xanthate filaments.

Having thus described my invention, I claim:

1. A process of making alcoholized modified cellulose characterized by improved resistance against attack by hot dilute aqueous alkalies, as compared with hydrocellulose of the same fluidity, and characterized by a copper number less than one, comprising: subjecting substantially dry cellulose to the action of an alcoholic solution containing an acid 01' the group consisting of sulfuric, hydrochloric, and para-toluene sulfonic acid, said solution containing no more than 2 percent of water, the acid concentration in the alcohol being no greater than 2-normal, the alcohol being a primary alcohol taken from the group consisting of lower primary alkanols and benzyl alcohol, the cellulose being subjected to the simultaneous action of the acid and alcohol, and maintaining them in contact at least until substantially maximum fluidity of the product is attained and until an alcoholized cellulose having a copper number less than one is formed.

2. The process of claim 1 in which the cellulose is cotton, and the acidic alcoholic solution contains no more than one percent of water.

3. The process 01' claim 1 in which the cellulose is cotton, the alcohol is absolute ethanol, and the acid is HCl in less than one percent concentration.

4. The process or claim 1 in which the cellulose is cotton, the alcohol is absolute'methanol, and Number Name Date the acid is H01 in about 0.5 N concentration. 2,141,669 Richter et a1. Dec. 2'7, 1938 5. The process of claim 1 in which the cellulose 2,368,527 Edelstein Jan. 30, 1945 is mercerized cotton. 2,396,957 Lazier et al Mar. 19, 1946 6. The process of claim 1 in which the cellulose 5 is delignified wood. H R REFERENCES RICHARD REEVES- Wolfram et al., J. A. C. 8., vol. 59, page 282, 1937. Fischer (1), Berichte, vol. 26, page 2400, 1893. REFEREN ES CITED Fischer (2),- Berichte, vol. 27, wage 673, 1894. The following references are of record in the 10 Karrer, Organic Chemistry, Nordemann Pubfile of this patent: lishlng Co., Inc., New York, N. Y., 1938, pages UNITED STATES PATENTS 142-143 Number Name Date 2,139,302 De Booys Dec. 6, 1938 1a 

1. A PROCESS OF MAKING ALCOHOLIZED MODIFIED CELLULOSE CHARACTERIZED BY IMPROVED-RESISTANCE AGAINST ATTACK BY HOT DILUTE AQUEOUS ALKALIES, AS COMPARED WITH HYDROCELLULOSE OF THE SAME FLUIDITY, AND CHARACTERIZED BY A COPPER NUMBER LESS THAN ONE, COMPRISING: SUBJECTING SUBSTANTIALLY DRY CELLULOSE TO THE ACTION OF AN ALCOHOLIC SOLUTION CONTAINING AN ACID OF THE GROUP CONSISTING OF SULFURIC, HYDROCHLORIC, AND PARA-TOLUENE SULFONIC ACID, SAID SOLUTION CONTAINING NO MORE THAN 2 PERCENT OF WATER, THE ACID CONCENTRATION IN THE ALCOHOL BEING NO GREATER THAN 2-NORMAL, THE ALCOHOL BEING A PRIMARY ALCOHOL TAKEN FROM THE GROUP CONSISTING OF LOWER PRIMARY ALKANOLS AND BENZYL ALCOHOL, THE CELLULOSE BEING SUBJECTED TO THE SIMULTANEOUS ACTION O THE ACID AND ALCOHOL, AND MAINTAINING THEM IN CONTACT AT LEAST UNTIL SUBSTANTIALLY MAXIMUM FLUIDITY OF THE PRODUCT IS ATTAINED AND UNTIL AN ALCOHOLIZED CELLULOSE HAVING A COPPER NUMBER LESS THAN ONE IS FORMED. 